//
// GTMTypeCasting.h
//
// Copyright 2010 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License.  You may obtain a copy
// of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
// License for the specific language governing permissions and limitations under
// the License.
//

#import <Foundation/Foundation.h>
#import "GTMDefines.h"

// These are some basic macros for making down-casting safer in Objective C.
// They are loosely based on the same cast types with similar names in C++.
// A typical usage would look like this:
//
// Bar* b = [[Bar alloc] init];
// Foo* a = GTM_STATIC_CAST(Foo, b);
//
// Note that it's GTM_STATIC_CAST(Foo, b) and not GTM_STATIC_CAST(Foo*, b).
//
// GTM_STATIC_CAST runs only in debug mode, and will assert if and only if:
// - object is non nil
// - [object isKindOfClass:[cls class]] returns nil
//
// otherwise it returns object.
//
// GTM_DYNAMIC_CAST runs in both debug and release and will return nil if
// - object is nil
// - [object isKindOfClass:[cls class]] returns nil
//
// otherwise it returns object.
//

// Support functions for dealing with casting.
GTM_INLINE id GTMDynamicCastSupport(Class cls, id object) {
  _GTMDevAssert(cls, @ "Nil Class");
  return [object isKindOfClass : cls] ? object : nil;
}

GTM_INLINE id GTMStaticCastSupport(Class cls, id object) {
  id value = nil;

  if (object) {
    value = GTMDynamicCastSupport(cls, object);
    _GTMDevAssert(value, @ "Could not cast %@ to class %@", object, cls);
  }
  return value;
}

#ifndef GTM_STATIC_CAST
# ifdef DEBUG
#  define GTM_STATIC_CAST(type, object) \
  GTMStaticCastSupport([type class ], \
    object)
# else
#  define GTM_STATIC_CAST(type, object) ((type*)(object))
# endif
#endif

#ifndef GTM_DYNAMIC_CAST
# define GTM_DYNAMIC_CAST(type, object) \
  GTMDynamicCastSupport([type class ], \
    object)
#endif
